U.S. Pat. No. 6,492,758 describes an electronically commutated transverse flux motor having a multiple phase stator. The stator is formed from two complementary facing pieces each carrying half the stator poles that are designed in the manner of claw poles. The stator windings are sandwiched between these two pieces and are encompassed by the opposing claw poles. In this document, the advantages of transverse flux machines are touched on briefly. A transverse flux machine is capable of producing power densities that are several times greater than conventional radial flux machines. This arises from the geometry of transverse flux machines which makes it possible to have a larger number of poles while maintaining the same magnet-to-magnet force per pole than would be possible in a conventional machine. Due to their three dimensional geometric form, however, it is difficult to construct transverse flux machines using standard core lamination techniques, since a laminated stator body would impede the necessary three-dimensional magnetic flux. This difficulty is overcome in U.S. Pat. No. 6,492,758 by the use of sintered powdered iron cores.
For transverse flux machines having a claw pole stator, it is basically known in the prior art to make both the stator back yoke as well as the claw poles out of iron or out of soft magnetic composite materials, particularly powders.
U.S. Pat. No. 6,236,131 describes a different type of transverse flux machine having U-shaped and I-shaped back yokes and a rotor that is made up, as in conventional radial flux machines, of a rotor-back yoke ring and permanent magnets attached thereon. The U-shaped back yokes and the I-shaped back yokes can be manufactured using well-known core lamination techniques, although in practice it is difficult to secure the individual U-shaped and I-shaped back yokes. For this purpose, usually non-magnetic holding pieces are needed to fasten the I-shaped back yokes.